Beneficiation of iron ores



' Patented Apr. 3, 1951 2,547,148 BENEFICIATION OF IRON ORES William A. Bates, Berkeley, Calif., assignor to California Research Corporation, San Fran-" cisco, Calif., a corporation of Delaware No Drawing. Application February 18, 1949, Serial No. 77,270

12 Claims. (c1. 209-166) 1 This invention relates to a process for beneficiating iron ores. More particularly, it relates to a process for beneficiating low-grade iron oxidebearing ores by a sequence of steps of conditioning and froth flotation of ore pulps with the aid 'of a new and effective collecting agent produced by sulfonating a particular type of polyalkylated aromatic hydrocarbons. In'the course of the last few decades, deposits of high-grade iron ore have been diminishing at 'a rapid rate owing to the steadily increasing demand of expanding manufacturing industries.

future. Whenever the siliceous impurity is not completely leached out owing to the particular nature of the ore involved, or because of some other factors, additional beneflciation may be 58- cured by physical separation processes such as screening, log-washing, classification, heavy media separation, jigging, etc. Unfortunately,

these processes are generally ineffective with materials finer than about 65 mesh in size, and thus -a large proportion of the weight of the ore must be discarded and is lost as tailings containing from about 50 to 60% of the weight of the original iron.

In view of the growing scarcity of high-grade iron ores suitable for direct shipment to the smelters, the problem of developing efiicient methods of beneficiating the low-grade iron oxide-bearing wash-ores and jig-ores, as well as the heretofore unused low-grade iron formations found in nature, such as taconite, acquires great importance.

My invention offers a simple and economical process for beneficiating low-grade iron ores by the application of a new and effective collecting agent for froth flotation of iron oxide material from such ores. It permits of effectively recovering iron oxides from ore fines such as are obtained in the overflow of iron washer plants and in the rejected'waste products from heavy media separation, and, in general, from ores which have been comminuted, as by grinding, in order-to 2 unlock the iron mineral from its surrounding gangue. I

The description which follows teaches the preparation of my new collecting agent and the method of applying it to ore pulps in order to obtain optimal iron recoveries from th froth flotation of low-grade iron ores.

As mentioned hereinbefore, in its general aspects my invention relates to the flotationof particles of iron oxide mineral with the aid of a collecting agent obtained by sulfonation of a certain type of polyalkylated aromatic hydrocarbons. These polyalkylated aromatic hydrocarbons are the bottoms fraction from the alkylation of mononuclear aromatic hydrocarbons such as benzene, toluene, or a Xylene, with olefins, or olefin-polymers,-containing from 9 to 18 carbon atoms and boiling between about 250 F. to about 585600 F., and preferably with those containing'frorn 12 to 15 carbon atoms and boiling betweenabout 350 F. to about 520 F. Polymers of propylene or butylene, or mixtures of propylene and butylene polymers, are particularly satisfactory for the purpose, although other olefins containing from 9 up to 18 carbon atoms and boiling between about 250 F. to about 600 F., for instance, those olefins obtainable by the Fischer-Tropsch synthesis, may also be used for the alkylation of the aromatic nucleus. In the preparation of olefin polymers suitable for the alkylation-of aromatic hydrocarbons, purity of the olefin stock: is'not essential; thus, for instance, instead of substantially pure propylene, mixtures of propylene with saturated low molecular weight hydrocarbons,

and ,even those mixtures containing some ethylaromatic hydrocarbons under alkylating conditions in the presence of a catalyst such as hydrogen fluoride or boron trifluoride'or of other suit able alkylation catalysts, and in such a way as to group. The resulting alkylat is fractionated in order to remove excess unreacted aromatic hydrocarbon and fractions boiling between about 175 F. and about 600 F. The remaining bottoms fraction consists of polyalkylated mononuclear aromatic hydrocarbons boiling above the boiling point of a monoalkylated aromatic hydro of a catalyst.

.acid per l mol of polyalkylated benzene.

carbon in which the alkyl portion corresponds to the olefin employed for alkylation. This bottoms fraction is withdrawn to be converted by sulfonation into the collecting agent of the present invention.

The sulfonation treatment of these polyalkylated aromatic bottoms is effected in a suitable apparatus with strong (fuming) sulfuric acid at a temperature below about 160 F., the acid being employed in an amount suited to th particular requirements of each case, and preferably in amounts from about 3 to about 20 mols of the acid per 1 mol of the polyalkylated aromatic hydrocarbon bottoms. A mixtur of polyalkylated mononuclear aromatic sulfonic acid and of sulfuric acid is obtained. Th polyalkylated mononuclear aromatic sulfonic acid in this mixture is not water-soluble, but only water-dispersible.

However, this fact does not affect the efiectiveness of the sulfonic acid as a collecting agent when the mixture of acids is employed in the froth flotation of iron oxide ores;

Olefin polymers suitable for the allrylation of mononuclear aromatic hydrocarbons which. are to be converted by sulfonation into collecting agents of my inventionare produced by polymerizing olefins, such as propylene, in the presence Generally, an acid polymerization catalyst, such as a phosphoric acid catalyst will beused.

In the preferred embodiment of the preparation of flotation agentsof my invention, substantially pure propylene is polymerized at a temperature from about375 F. to about 475. F. and a pressure, e. g., from about 200 to about 600 p. s. i.,-in the presence of a catalyst consisting of a charcoal support saturated with orthophosphoric' acid.- The resulting product is a polypropylene boiling between about 65 F. and about .50" and about 100 F., molar excess of benzene over polypropylene, and a large amount of the catalyst (from 200 to 800 mol per cent of hydrogen fluoride) based on the polypropylene feed.

The alkylate is then distilled to remove excess benzene and lighter alkyl aromatic hydrocarbons boiling up to about 500 F., followed by the socalled' heart out which boils between about 500 F. to about 600 F. and consists predominantly of monoalkylated aromatic hydrocarbons having .from- 12 to 15 carbon atoms in the alkyl' chain.

The remaining heavy bottoms fraction boiling above 600 F. and up to about 725 F. is a polyalkylatedbenzene fraction and consists-predominantlyof paradialkyl benzenes. It is sulfonated 'ina suitable apparatus with- 20% fumingv sulfuric acid in aratio of about 3 to about 20 molsv of the The ultimate sul-fonation product is a mixture; of a substantially water dispersible polyalkylated mononuclear aromatic sul-fonic acid and sulfuric acid.

Hereinafter in this specification-whenever the term-sulfonic acid collecting agent or collector is mentioned, it will designate the mixture of polyalkylated mononuclear aromatic sulfonic acid and sulfuric acid as obtained by sulfonating the bottoms fraction of polyalkylated aromatic hydrocarbons, suchas paradialkyl benzenes, in

accordance with the process described hereinabove. Accordingly, the amounts of sulfonic acid given in the following description and in the tables will represent the content of polyalkylated mononuclear aromatic sulfonic acid in the sulfonation reaction mixture.

In recovering iron oxide materials from the low-grade iron ores, such as wash-ore tailings, in accordance with the invention, an aqueous free-flowing ore pulp is formed and subjected first to a desliming treatment, in order to remove the extremely fine colloidal slime material of less than about 18-20 microns insize- This deslimin treatment may be effected by any of the conventional methods of the art, for instance, by employing a hydroseparator followed by a bowl classifier; The deslimed pulp containing preferably about 25% by weight solids is then ready for conditioning and flotation in accordance with the process of my invention.

The conditioning of the iron ore pulp ordinarily' is carried out at high dilution (of the order of 25% solids). Usually it is preferred to effect flotation in an acid circuit. Should the sulfonic acid-sulfuric acid mixture fail to impart sufficient acidity corresponding to a pH of about 2 to 4 to the ore pulp, additional sulfuric acid may be added during the conditioning treatment'to insure the desired pH in the flotation circuit. Conditioning of the ore pulp at high dilution, however, is not always necessary for an effective flotation, and in certain cases, depending on the nature of the ore and other circumstances, it may be desirable to conditionthe ore pulp at a much lower dilution. (as high as 60 to 75% solids by weight of the pulp), and then to dilute the conditioned pulp to the desired flotation density of not less than 20% solids by weight of the pulp. Conditioning of the ore-pulp is effected in special conditioning or mixing'vessels; however, if so desired under the circumstances of a particular case, the various flotation reagents may be added directly into flotation cells or at various points during the flotation treatment.

In the practice of my invention the collecting efiect of the sulfonic acid collector is further enhanced by the addition of an unsaponifiable, nonvolatile hydrocarbon oil.

This unsaponifiable non-volatile hydrocarbon oil is preferably a neutral, petroleum hydrocarbon oil, such as a furnace oil or a fuel oil having an A. P. I. gravity from about 30 to about 35, although heavier oils having an A. P. I. gravity as low as 10 are also satisfactory. Petroleum oils are preferred because of their availability and relative cheapness, but other hydrocarbon oils which are non-volatile and unsaponifiable under the conditions of use in accordance with the invention may also beutilized.

In conditioning the ore pulp, the admission of the sulfonic acid collecting agent into the pulp is. followed by the addition of a neutral hydrocarbon oil. The relative proportions. of the sulfonic acid collector and of the hydrocarbon oil depend on the type of ore being treated, its structure (crystallinity) and the quantity of fines and slimes in the ore. Ordinarily, good results are obtained by employing a polyalkylated. mononuclear aromatic sulfonic acid collecting agent in amounts from about 0.5 to about 4.5 pounds per aromatic bottoms.

may vary outside this range. Thus when the ore is unusually slimy, a greater content of polyalkylated mononuclear aromatic sulfonic acid up to 5 and 6 pounds per each ton of ore may be necessary. The optimum weight ratio of the sulfonic acid collecting agent to the neutral hydrocarbon oil for an effective flotation may vary from 1:1 to 4:1, depending on the nature of the ore to be treated and other conditions of each particular case.

As mentioned hereinbefore, whenever the sulfonic acid collector of the present invention is not sufliciently acid to impart the desired degree of acidity (pH from about 2 to about 4) to the ore pulp undergoing flotation treatment, additional sulfuric acid in amounts ranging from about 1 to about 4 pounds of sulfuric acid. per each ton of 7 the deslimed ore being conditioned may be added to secure the desired pH in the flotation circuit.

Other suitable collectors and flotation reagents such as frothers, promoters and the like may be employed in conjunction with the sulfonic acid collector of my invention for the purpose of recovering iron oxides by froth flotation in proportions which may be varied in accordance with the needs of each particular case.

At this point it may be noted that, contrary to previous experience of froth flotation, complete ,desliming is not necessary. In order to obtain the optimal results it is entirely sufflcient to remove slimes finer than about 10 microns in size.

ity=10 A. P. I.) per each ton of the ore. Since in this case the mixture containing the sulfonic In agreement with the'customary practice of froth flotation, the rougher concentrate from the first flotation stage which is seldom of the final grade may be cleaned and recleaned as many times as desired. Likewise, the tailings from the initial flotation treatment may be scavenged repeatedly to yield the maximum recovery of iron before being rejected as final tailings.

The operation of my invention and the advan- .tages secured thereby will be better understood pylene, the remainder being saturated low-boiling hydrocarbons 72.4%, butylene 0.5% and ethylene 5.5%. Polymerization is effected at about 375 F. and 250 pounds pressure in the presence of a catalyst formed by saturating acharcoal support with 75% orthophosphoric acid. Benzene is alkylated with the resulting ClZ-Clfi polypropylene in the presence of a hydrogen fluoride .catalyst and at a temperature of about 70 F.,

acid collector is not suificiently acid to impart the preferred pH of about 2 to about 4 to the flotation circuit, 3 pounds of sulfuric acid per each ton of ore is added to the pulp being conditioned. After conditioning for about 2 to 3 minutes, air is admitted into the flotation cell, and a froth rich in iron oxide is removed. This initial froth is subjected to a second flotation without additional reagents and yields the final concentrate.

Upon redistribution of the middling remaining as a residue from this second flotation or cleaning treatment, an ore concentrate is obtained which is equal to'23.1 of the weight of the original solid ore feed. and contains 59.1% iron. A

very satisfactory recovery of iron equal to 94.2% of the metal originally present in the dry feed is obtained. 7

Example II .--In this example, the same sulfonic acid collector as in Example I is employed to recover iron oxide material from a difficult type of weathered or painty ores. These ores are wash plant tailings containing hematite, limonite and. considerable quartz gangue stained with adherent iron oxide. This stained quartz is a particularly difiicult material to separate. An ore pulp formedrfrom 500 grams of such substantially deslimedtailings having an iron content equal to 23.7% by weight on dry deslimed basis contains 25% solids and is conditioned in a flotation cell for about 2 minutes with 3.5 pounds of the sulfonic acid collector, equivalent to 1.9 pounds of polyalkylated aromatic bottoms, 3 pounds of furnace oil having a gravity of 31 A. P. I., and 3 pounds of sulfuric acid per each ton of ore. Thereupon air is admitted into the cell, and the mineral-laden froth is removed. This flotation is repeated three times with no further addition of reagents. The concentrate obtained upon redistribution of the middling contains 60.5% iron and is equal to 35% of the weight of the original feed. The recovery of iron amounts to 89.1 of the metal originally present in the ore.

Example III.-In this test, the sulfonic acid collector is prepared by treating the polyalkylated aromatic bottoms fraction of Example I with 20 of deslimed weathered ore as in Example II is whereupon the bottoms fraction boiling above 600 F. is separated from excess benzene and the light heart cut. This polyalkylated aromatic bottoms fraction boils between 638 F. and 751 F. It is sulfonated at a temperature of "less than 160 F. with 20% fuming sulfuric acid in a mol ratio of 3 mols of acid per 1 mol of polyalkylated Wash plant tailings (500 grams), after removal of slimes finer than about 20 microns in size (slimes amounting to about 25-27% by weight based on dry ore), have an iron content of 14.5% by weight on "dry deslimed basis. This deslimed material is charged into a flotation cell with enough water to form a pulp containing 25% solids. The resulting ore pulp is then conditioned in this flotation cell by adding 2 pounds of the sulfonic acid collecting agent, prepared as described hereinabove and equivalent to 0.6 pound of polyalkylated aromatic hydrocarbons, followed by 3 poundsof fuel oil (gravintroduced in an amount equal to 500 grams into a flotation cell with sufiicient water to form a pulp containing 25% solids. After conditioning this pulp for 2 to 3 minutes with 3.5 pounds of the aforementioned sulfonic acid collector, equivalent to 1.3 pounds of polyalkylated aromatic hydrocarbons, followed by' 3 pounds of fuel oil having a gravity of 31 A. P. I., per each ton of dry ore, air is admitted into the pulp, and the iron oxidebearing froth is removed. In this instance, the ratio of the number of mols of sulfuric acid employed for sulfonation per each. mol of polyalkylated aromatic bottoms is sufficiently large to impart a pH of 2 to 4 to the flotation circuit, and thus no additional sulfuric acid is required inthe conditioning step. The froth product is cleaned by three successive flotations without further addition of the reagents. After redistribution of the middling, a recovery of 91.4% iron is secured in a concentrate product which analyzes to contain 60.5% iron and amounts to Example IV.--In this case, the deslimed ore and the reagents for the flotation thereof are similar to those of Examples II and III, except for the fact that the mol ratio of sulfuric acid to polyalkylated aromatic hydrocarbon bottoms in the preparation of the sulfonic' acid collector is 11.811. The product of this sulfonation in an amount equal to 3.5 pounds, equivalent to 0.86 pounds of polyalkylated aromatic bottoms, is added into the flotation cell, followed by 4.5 pounds of fuel oil (gravity=31 A. P. 1.), per each ton of the ore, and the conditioning and flotation treatments are carried out as indicated in the previous examples. The recovery of iron, aftenclistribution of the middling, is found to be equal to 95.5% of the original feed. The concentrate contains 60.0% iron and represents 36.2% of the weight of the original ore. The following Table I summarizes the data obtained in Examples I, II, III and IV.

TABLE I Data on flotation of wash plant tailings (500 grams, dcslimed) Example No I II III IV Molar ratio of sulfuric acid employed for sulfonation to polyalkylatedbenzenebottoms 3:1 3:1 :1 11.8:1 Reagents in Lbs/Ton of Ore:

Sulfonic acid c0l1ect0r. 2.0 3. 5 3. 5 3. 5 Neutral Hydrocarbon Oil (Fuel oil; gravity-=31 A. P. I. 3.0 3.0. 4.5 H 804 (96%) to secure desired pH 3.0 3.0 None None Feed: Iron content,

by'wcight 14.5 23. 7 22. 8 22. 7 Product (based on desllmed Iron content of final concentrate, in per cent I 59. l 60. 5 60. 5 60.0 Weight of final concentrate,

in per cent of feed 23. 1 35.0 34. 4 36. 2 Recovery of Iron, in per cent of feed 94. 2 89. 1 91. 4 95. 5

The next series of tests with a low-grade weathered iron-bearing ore (wash plant tailings) are made to illustrate the optimal operating conditions for the effective froth notation of iron oxides from iron-bearing ores in accordance with my invention. In these tests I have varied the type of polyalkylated aromatic hydrocarbon bottoms fraction employed for the preparation of the sulfonic acid collector, the mol ratio of sulfuric acid to polyalkylated aromatic bottoms, the amount of neutral hydrocarbon oil, the extent of desliming, and, in some tests, I have added a flotation activator to the ore pulp. Numerous test data defining these optimal conditions could be adduced, but it is believed that those several representative tests as are described and tabulated hereinafter will be sufficient.

The sulfonic acid collector for these tests illustrated in Tables II-V is obtained by sulfonating is suflicient to secure the desired pH of about 2 to about 4 in the flotation treatment. In most of thesetests', slimes finer'than' 10 microns in size are removed prior to the conditioning treatment, unless otherwise indicated, and all the material coarser than 65 mesh is eliminated by screening. As will be shown further on in Table II, it is unnecessary to remove slime particles larger than 10 microns in size to insure satisfactory recovery of iron values. On the other hand, desliming to less than 10micron size will ultimately result in unsatisfactory flotation. For the sake of stability and ease in dispensing, the sulfonic acidsulfuric acid mixture is diluted with water in a concentration equivalent to 0.0625 gram of polyalkylated benzene bottoms per one milliliter of diluted solution prior to the conditioning of the ore pulp.

The ore is submitted to the following sequence of treating steps: (1) desliming to a desired degree; (2) elimination of material coarser than 65 mesh by screening; (3) formation of an aqueous iron ore pulp; l) conditioning of this ore pulp at flotation density (of the order of 25% solids) and (5) froth flotation of the conditioned iron ore pulp in successive flotation cells. As pointed out already, the rougher concentrate is seldom of the final grade and, therefore, it is submitted to three stages of cleanings, yielding the final concentrate and the cleaner tailings which are returnable to the process. The rougher tailings are scavenged as frequently as desired and yield a low-grade scavenger concentrate likewise returnable to the process. In some cases, an additional flotation step is interposed between the rougher and the scavenging treatment to produce a middling which may also be retreated at least once to prevent build-up of middlings.

Table II below combines the data on the reagents used for flotation, the procedure followed, and the results obtained by employing a sulfonic acid collector produced by sulfonation of undistilled polyalkylated benzene bottoms boiling between 603-700 F., a 50% overhead fraction thereof boiling between 603-665 F. and a 75% overhead fraction boiling between 603684 F. It is noted that the weight recovery and the metal recovery of the product are substantially increased by employing the fraction boiling between 603-684 F. The grade of the product is likewise improved.

TABLE II Effect of boiling range of polyalkylaied benzene bottoms employed to prepare salfom'c acid collector on recoveries of iron by flotation Test No Boiling range of polyalkylated benzene bottoms F 603-700 603665 603-684 Molar ratio of sulfuric acid employed for sulfonation to polyalkylated benzene bottoms.-. 10:1 10:1 10:1 Reagents in Lbs/Ton of Ore:

H 50 (20% fuming) employed for sulfonation 8. 4 5. 5 8. 4 Sulfonic acid collector 3.7 2. 45 3. 7 Neutral hydrocarbon oil (Furnace oil of 31 API gravity) 1 5 -4. 0 0 Feed:

Maximum size of slimes removed, in

microns 25 25 25 Iron content, in per cent 22.8 22. l 22. 1 Product (Based on Deslimed Feed):

Iron content of final concentrate, in

per cent 53. 4 59. 5 58. 5 Weight of final concentrate, in per cent of feed 25.0 30. 8 33. 6 Recovery of iron, in per cent of feed" 58. 5 83. 0 88. 9

' tensive desliming treatment is not critical for a satisfactory iron oxide recovery, and that the best recoveries are obtained upon removal of slimes not larger than 10 microns in size.

TABLE III.

Effect of molar ratio of sulfuric acid to polyallcylated benzene bottoms and of degree of desliming on recoveries of iron oxide from lowgrade iron ore Test N o 185 187 174 155 Molar ratio of sulfuric acid employed for sulfonation to polyalkylated benzene bottoms 10:1 6:1 10:1 10:1 Reagents in Lbs/Ton of Ore:

H280; employed for sulfonation (20% fumin 11.7 '7.8 9.8 12.2 Sulfom'c acid collector 4. 29 4. 29 4. 29 2. 45 Neutral hydrocarbon oil (furnace oil of 31 API gravity) 7. 7. 0 7. 0 5.0 Feed:

Maximum size of slimes removed, in

microns 10 V 25 Iron content, in per cent 24. 4 25. 2 22.0 Product (based on deslimed feed): I

Iron content of final concentrate, in

per cent 61. 1 60.4 7 2 Weight of final concentrate, in pe cent of feed 38.2 36.2 42.4 37.1 Recovery of iron, in per cent of feed 96. 1 89. 5 95. 5 94. 0

fonic acid collector upon the recovery of iron oxides from the ore by the process of the presentinvention. It is noted that an increase in the amount" of hydrocarbon oil substantially improves the recovery of iron and tends to raise the grade of the concentrate.

TABLE IV Efiect of varying amounts of neutral hydrocarbon oil on recovery oj-- iron orev Test No 138-3 1384 155 158 Molar ratio of sulfuric acid to polyalkyv lated benzene bottoms :1 10:1 10:1 10:1 Reagents in Lbs/Ton of Ore:

H2804 employed for sulfonation fuming) 5. 5 5. 5 9. 6 12. 2 Sulfonic acid collector 2. 4 2. 2. 45 2. 45 Neutral hydrocarbon oil (Furnace oil: Gravity=p31 API) 1.5 4.0 5.0 7.0 Feed: Maximum size of slimes removed in 7 microns 25 25 2 25 Iron ccnten in percen 21. 9 21. 7 22.0 22. 6 Product (based on deslimed feed Iron content of final concentrate, in

per cent 54. 6 57. 2 60. 0 Weight of final concentrate, in per cent of iced 32.4 34.2 37.1 35.4 Recovery of iron, in per cent of feed 80. 5 85. 7 94. 0 94. 1

Table V contains the results of tests with and Molar ratio of sulfuric acid to FeCla activator 10 TABLE v Efiect of addition of FeCl: on flotation results Test No 162 178 164 polyalkylated benzene bottoms Reagents in Lbs/Tons of Ore:

H SOl employed for sulfonation (20% fumm sulf nic acid collector Neutral hydrocarbon oil (Furnace oil:

Gravity=31 API) Feed:

Size of slimes removed, in microns Iron content, in per cent Product (based on deslimed feed):

Iron content of final concentrate, in per cent- Weight of final concentrate, in per cent of feed Recovery of iron, in per cent of feed Table VI provides a comparison between the flotation results obtainable with the sulfonic acid collector of the present invention and the results obtained by employing a well-known col-- lector of cationic type, namely, normal dodecyl amine acetate, which floats the quartz away from hematite in taconite or in a similar low-grade iron ore.

TABLE VI Comparison of flotation results obtained with a cationic collector Test N 163 210. 4

Molar, ratio of sulfuric acid employed for sulfonation to polyalkylated benzene bottoms 10 :1 Reagents in Lbs/Ton of Ore:

H1504 employed for sulfonation (20% fuming) 10. 4

Sulfonic acid collector 3. 7 Furnace oil (Gravity=3l API) 6 0 Methyl amyl alcohol frother--- 0. 1 Dodecyl amine acetate 1. 8

Feed:

Maximum size of slimes removed, in microns. l0 15 Iron content, in per cent 23. 6- 23. 4

Product (based on deslimed feed):

Concentrate grade, per cent Fe 61. 5 49. 8 Weight of concentrate, in per cent of feed 34.2 19. 8 89. 1 r 42. l

without iron chloride as an activator of flotation.

It is observed that the presence of about 2 to 5 pounds of iron chloride per ton of ore improves Recovery of Fe, in per cent The above data show a definite superiority of flotation agents containing the sulfonic acid collector of my invention over the cationic dodecyl amine acetate collector with respect to the weight of final concentrate recovered, the amount of iron recovery in'per cent of the feed and the grade of the final concentrate.

The last Table VII contains a comparison of test results from froth flotation of iron ore of approximately the same grade in accordance with the present invention [Tests (b) and (9)]. and also by employing other collecting agents used in the art, such as water-soluble and oilsoluble petroleum sulfonates, unsulfonated tall oil, unsulfonated tall oil plus a. normal alkyl amine, and normal dodecyl betaine. The examination of the data assembled in this table defnitely shows that the results obtained with my sulfonic acid collector are superior to those 0btainable with other collecting agents. For an equivalent grade of the ore, the sulfonic acid collector of my invention secures superior recoveries. Thus, it is found that the sulfonic acid collector provides an economical and efiective means for the recovery of iron oxide from ores, particularly from low-grade iron ores, and

that the application of this collector in froth flotation yields high-grade final concentrates and secures recoveries which compare advantageously with the other flotation processes of the art.

12 froth flotation is effected at a dilution of the ore pulp corresponding to not less than 20% solids.

7. A process as definedin claim 1, wherein said froth flotation is effected in the presence of TABLE VII Comparison with various collectors Grade of Final Recovery, Test Type of Ore Type of Process Collecting Agent Employed g eg gggggy gagegg (41).--. Wash Ore, 17.7% Fe Cationic; silicaremovaL N-dodecyl betaine 0.48 Average 56.9 75 (b) Wash Ore, 24.3% Fe Anionic; iron oxide re- Polyalkylated benzene sulfonic 4.3 sulfom'c acid+7.0 1 96.1

moval. acid collector+neutral oil. oil. Wash Ore, 20.2% Fe Petrlolgillm sulionate (water- 1.96 60. 2 85.0

so u e (d), Wash Ore, 19.6% Fedo Petroleumsulfonate(oil-soluble) 2.90 58. 2 35.5 (e).. Wash Ore, 23.8% Fe-.- Combined anionic and Tall oil-i-C amine 1.5 tall oil+0,l0 amine 57. 2 33. 9

cationic. (f)-- Wash Ore, 21.7% Fe Anionic; silica removaL Tall oil A 2.00.. 59. 2 82.3 (g) Wash Ore, 22% Ben", .d Polyalkylatcd benzene sulfonic 2.45 sulfonic acid-km) 57. 2 94.0

acid col1ector+neutrel oil. oil.

The application of my novel sulfonic acid collector is by no means limited to the recovery of hematite and magnetite. Other iron minerals such as martite, limonite, siderite, goethite and the lik may be also successfully floated in accordance with this invention. Generally speaking, the application of my sulfonic acid collector permits of recovering commercially acceptable concentrates from tailings heretofore rejected in the conventional processes of iron-ore beneficiation.

In conclusion, it is to be understood that the test data in th aforegiven examples and tables are merely illustrative, and that the invention is not limited thereby, but only by the definitions of the appended claims. 7

1. A process for the recovery of iron oxide minerals from iron-bearing ores, which comprises forming an aqueous pulp of an iron oxide-bearing ore and effecting froth flotation of said aqueous pulp in the presence of a polyalkylated mononuclear aromatic sulfonic acid, said acid being a sulfonated bottoms fraction from the alkylation of a mononuclear aromatic hydrocarbon with an olefin containing from 9 to 18 carbon atoms and boiling between about 250 F. to about 600 F., said bottoms fraction boiling above the boiling point of a monoalkylated aromatic hydrocarbon in which the alkyl portion corre sponds to said olefin.

2. A process as defined in claim 1, wherein the ore pulp subjected to froth flotation has a pH from about 2 to about 4.

3. A process as defined in claim 6, wherein said froth flotation is effected in the presence of said polyalkylated mononuclear aromatic sulfonic acid and of an unsaponifiable nonvolatile hydrocarbon oil.

4. A process as defined in claim 1, wherein said froth flotation is eifected in the presence of said polyalkylated mononuclear aromatic sulfonic acid and of a neutral petroleum hydrocarbon oil characterized by a gravity from about to about A. P. I.

5. A process as defined in claim 1, wherein said froth notation is effected in the presence of said polyalkylated mononuclear aromatic sulfonic acid and or" a neutral nonvolatile petroleum hydrocarbon oil, and wherein the ratio of said polyalkylated mononuclear acid to said neutral petroleum hydrocarbon oil is comprised between 1:1 and 4:1.

6. A process as defined in claim 1, wherein said aromatic sulfonic sufiicient sulfuric acid to impart a pH of about 2 to about 4 to the ore pulp.

8. A process as defined in claim 1, wherein said olefin is an olefin containing from 12 to 15 carbon atoms and said mononuclear aromatic hydrocarbon is benzene.

9. A process as defined in claim 1, wherein said olefin is a polymer of propylene containing from 12 to 15 carbon atoms and said monoe nuclear aromatic hydrocarbon is benzene.

10. A process for the recovery of iron oxide minerals from iron-bearing ores, which comprises forming an aqueous pulp of an iron oxide-bearing ore, removing colloidal slimes therefrom, condi- 'tioning the deslimed aqueous ore pulp with a polyalkylated mononuclear aromatic sulfonic acid, said acid being a sulfonated bottoms fraction from the alkylation of a mononuclear aromatic hydrocarbon with an olefin containing from 9 to 18 carbon atoms, said bottoms fraction boiling above the boiling point of a monoalkylated aromatic hydrocarbon in which the alkyl portion corresponds to said olefin, effecting froth flotation of the conditioned ore pulp in an acid circuit having a pH from about 2 to about 4, and recovering the iron oxide-bearing froth.

11. A process as defined in claim 10, wherein the colloidal slimes removed are slimes less than 10 microns in size.

12. A process for the recovery of iron oxide minerals from iron-bearing ores, which comprises forming an aqueous pulp of an iron-bearin ore, conditioning said pulp at low dilution corresponding to 75% or less solids with a polyalkylated mononuclear aromatic sulfonic acid, said acid being a sulfonated bottoms fraction from the alkylation of a mononuclear aromatic hydrocarbon with an olefin containing from 9 to 18 carbon atoms and boiling between about 250 F. to about .600 F., said bottoms fraction boiling above the boiling point of a monoalkylated aromatic hydrocarbon in which the alkyl portion corresponds to said olefin, and effecting froth flotation of the conditioned pulp at high dilution of not less than 20% solids.

WILLIAM A. BATES.

REFERENCES CITED UNITED STATES PATENTS Name Date Brandt Sept. 26, 1944 Number Re. 22,548

UNITED STATES PATENTS Number Name Date Handy June 27, 1939 Reid May 28, 1940 Gaylor Feb. 4, 1941 Booth et a1 Sept. 18, 1945 Booth Oct. 29, 1946 Booth et a1 Oct. 29, 1945 Number 

1. A PROCESS FOR THE RECOVERY OF IRON MINERALS FROM IRON-BEARING ORES, WHICH COMPRISES FORMING AN AQUEOUS PULP OF AN IRON OXIDE-BEARING ORE AND EFFECTING FROTH FLOATION OF SAID AQUEOUS PULP IN THE PRESENCE OF APOLYALKYLATED MONONUCLEAR AROMATIC SULFONIC ACID, SAID ACID BEING A SULFONATED BOTTOMS FRACTION FROM THE ALKYLATION OF A MONONUCLEAR AROMATIC HYDROCARBON WITH AN OLEFIN CONTAINING FROM 9 TO 18 CARBON ATOMS AND BOILING BETWEEN ABOUT 250* F. TO ABOUT 600* F., SAID BOTTOMS FRACTION BOILING ABOVE THE BOILING POINT OF A MONOALKYLATED AROMATIC HYDROCARBON IN WHICH THE ALKYL PORTION CORRESPONDS TO SAID OLEFIN. 